2024

2024/03/findings.md

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+# Day 3
+
+Of course 1 min of regex freestyle (`mul\(\d+,\d+\)`) and it would have been done, i wanted to do it on my own.
+NVM did it with Regex xD
+
+Part 2 was fun, I basically computed an array of the `do()` and `don't()` index and simply looked up which one was further up.
+
+## Other ways
+
+I think a way more efficient way to go about it would to take more of a scan approach, where we keep track of the enabled/disabled status and parse as we go.

2024/03/main.py

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+import re
+
+re_mul = re.compile(r"mul\(\d+,\d+\)")
+re_enable = re.compile(r"do\(\)")
+re_disable = re.compile(r"don't\(\)")
+
+
+def solve(raw: str) -> int:
+    # Part 1
+    part1 = 0
+    part2 = 0
+
+    enable = [m.end() for m in re_enable.finditer(raw)]
+    disable = [m.end() for m in re_disable.finditer(raw)]
+    for match in re_mul.finditer(raw):
+        # Part 1
+        [left, right] = match.group()[4:-1].split(",")
+        result = int(left) * int(right)
+        part1 += result
+
+        # Part 2
+        s = match.start()
+        last_enable = 0
+        for x in enable:
+            if x > s:
+                break
+            last_enable = x
+        last_disable = 0
+        for x in disable:
+            if x > s:
+                break
+            last_disable = x
+
+        disabled = last_disable != 0 and last_disable > last_enable
+        if disabled:
+            continue
+        part2 += result
+    return (part1, part2)
+
+
+# Test
+with open("./2024/03/test.txt", "r") as f:
+    result = solve(f.read().strip())
+    print(result)
+
+# Input
+with open("./2024/03/input.txt", "r") as f:
+    result = solve(f.read().strip())
+    print(result)